Taanis 2:6-7

On the first three fasts, the kohanim on duty at the Temple that week fasted but not all day; the kohanim serving that day did not fast at all. On the second three fasts, the kohanim on duty that week fasted all day and the kohanim serving that day fasted but not all day. On the last seven fasts, both groups of kohanim fasted all day; this is the opinion of Rabbi Yehoshua. The Sages, however, say that none of these kohanim kept the first three fasts; on the second set of three fasts, the kohanim on weekly duty fasted but not all day and the kohanim serving that day did not fast at all; on the last seven fasts, the kohanim on weekly rotation fasted all day and those serving that day fasted but not all day.

Taanis 2:7

The kohanim on weekly rotation may drink wine at night but not during the day; those serving that day may not drink it by day or by night. The kohanim on weekly rotation and the men of the maamad (Israelites on duty in Jerusalem) may not shave their beards or wash their clothes during their week of service except on Thursday, in honor of Shabbos.